402 BACTERIOLOGY. 



those animals, and that this product by its presence 

 prevents the development of the same organisms if they 

 should subsequently gain access to the body. 



Bearing upon this view the experiments of Sirotinin,' 

 made with cultures of various pathogenic bacteria, 

 demonstrated that in so far as culture experiments were 

 concerned the only substances produced by growing 

 bacteria that could be in any way inimical to "their 

 further development were substances that gave rise to 

 alterations in the reaction of the medium in which 

 they were developing, i. e., acids or alkalies produced 

 by the bacteria themselves. So long as the organisms 

 were not actually dead from exposure to these substances, 

 correction of the abnormal reaction was followed by 

 further development of the organisms. Sirotinin. also 

 states that materials containing the products of growth 

 of bacteria, so long as they are maintained at a neutral 

 or only slightly alkaline reaction, serve very well as 

 media upon which to cultivate again the same organism 

 that produced them, providing the nutritive elements 

 have not been entirely exhausted. He remarks : that if 

 in such a concentrated form as we find the life-products 

 of bacteria in the medium in which they are growing, 

 no inhibitory compounds beyond acids and alkalies are 

 to be detected, it is hardly probable that they are pro- 

 duced in the tissues of the living animal, and retained 

 there, to a degree sufficient to prevent the growth of bac- 

 teria that may subsequently gain entrance to these 

 tissues, after the disappearance of the organisms con- 

 cerned in the primary invasion. On the other hand, 

 Salmon and Smith,^ Roux and Chamberland,^ and 



1 Zeitschr. fiir Hygiene, Bd. iv., 1888. 



2 Proc. of the Biol. Soc, Washington, D. C, 1886, vol. Hi. 

 s Annales de I'lnstitut Pasteur, tomes i , 11., 1888-89. 



